Metered dose medicament inhalers are well known for dispensing medicament to the lungs of a patient, for treating asthma for example. Existing types of medicament dispensing inhalers include pressurized propellant inhalers, aqueous solution inhalers, and dry-powdered inhalers.
U.S. Pat. No. 5,503,144 to Bacon, for example, shows a dry powdered inhaler. The inhaler includes a reservoir for containing a dry powdered medicament, a metering chamber for removal of the powdered medicament from the reservoir in discrete amounts, and an air inlet for entraining the removed powdered medicament through a mouthpiece upon patient inhalation.
Another example is U.S. Pat. No. 5,971,951 to Ruskewicz, which shows an inhaler including a motor driven cam mechanism for extruding aqueous medicament through a porous membrane to form a medicament aerosol for inhalation by a patient. The inhaler also includes sensors, circuitry and a microprocessor that determines the rate of patient inhalation and operates the extrusion mechanism only upon adequate inhalation levels.
A pressurized propellant, or “aerosol” inhaler is shown in U.S. Pat. No. 5,447,150 to Bacon, which also discloses a simple, mechanical actuation assembly for ensuring that medicament is dispensed from the inhaler only upon adequate inhalation by a patient. The actuation assembly works by applying a pre-load to a valve of the aerosol container sufficient to cause a dose release, but prevents the release by applying a pneumatic resisting force. The dose of medicament is then released upon a patient inhalation strong enough to move a door within the assembly, which in turn releases the pneumatic resisting force.
What is still desired, however, is a new and improved inhaler for administering medicament for patient inhalation. Preferably, the new and improved inhaler can be used with dry powdered medicament. In addition, the new and improved inhaler will preferably include mechanical assemblies for metering doses of medicament, managing medicament reservoir pressure, and counting the number of doses remaining in the inhaler.